1291221209 has 4 divisors (see below), whose sum is σ = 1359180240. Its totient is φ = 1223262180.

The previous prime is 1291221193. The next prime is 1291221293. The reversal of 1291221209 is 9021221921.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 1291221209 - 2⁴ = 1291221193 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1291221809) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 33979487 + ... + 33979524.

It is an arithmetic number, because the mean of its divisors is an integer number (339795060).

Almost surely, 2^1291221209 is an apocalyptic number.

1291221209 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

It is an amenable number.

1291221209 is a deficient number, since it is larger than the sum of its proper divisors (67959031).

1291221209 is an equidigital number, since it uses as much as digits as its factorization.

1291221209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67959030.

The product of its (nonzero) digits is 1296, while the sum is 29.

The square root of 1291221209 is about 35933.5666056126. The cubic root of 1291221209 is about 1088.9306373927.

The spelling of 1291221209 in words is "one billion, two hundred ninety-one million, two hundred twenty-one thousand, two hundred nine".